Television ratings information is typically generated by collecting viewing records or other viewing information from a group of statistically selected households. Each of the statistically selected households typically has a data logging and processing unit commonly referred to as a “home unit.” The home unit is often in communication with a variety of attachments that provide inputs to the home unit or receive outputs from the home unit. For example, a source identification unit such as a frequency detector attachment, which is a well-known device, may be in communication with a television to sense a local oscillator frequency of the television tuner. In this manner, the frequency detector attachment may be used to determine if the television is operating (i.e., is turned on) and to determine to which channel the television is currently tuned based on a detected frequency. A people counter, which is also a well-known device, may be located in the viewing space of the television and in communication with the home unit, thereby enabling the home unit to detect the identities of the persons currently viewing programs displayed on the television.
The home unit usually processes the inputs (e.g., channel tuning information, viewer identities, etc.) from the attachments to produce viewing records. Viewing records may be generated on a periodic basis (i.e., at fixed time intervals) or may be generated in response to a change in an input such as, for example, a change in the identities of the persons viewing the television, a change in the channel tuning information (i.e., a channel change), etc. In any case, each viewing record typically contains channel information such as a station or channel number and a time (e.g., a date and time of day) at which the channel was viewed. Of course, viewing records may contain other information such as the identities of viewers present at the viewing time.
Often, the home unit collects a quantity of viewing records and transmits collected viewing records, usually daily, to a central office or data processing facility for further processing or analysis. The central data processing facility receives viewing records from home units located in some or all of the statistically selected households and analyzes the viewing records to ascertain the viewing behaviors of a particular household or a particular group of households selected from all participating households. Additionally, the central data processing facility may generate viewing behavior statistics and other parameters indicative of viewing behavior associated with all of the participating households.
To generate viewing behavior information from viewing records, the central office or data processing facility compares reference data such as a list of programs (i.e., a schedule of television programming or television guide) to the viewing records. In this manner, the central office can infer which program was viewed by matching the time and channel information in a viewing record to the program associated with that same time and channel in the program schedule. Such a matching process can be carried out for each of the viewing records received by the central office, thereby enabling the central office to reconstruct what programs were watched by all participating households and the times at which the programs were watched.
While known apparatus and techniques for ascertaining the viewing behavior of a large population are well suited for viewing records associated with live viewing of television programming, these techniques are not suitable for use with audio and video programs that are recorded and then later viewed. In particular, for pre-recorded program information, the viewing time is delayed with respect to the time at which the program information was available as a live program. As a result, viewing records containing viewing time information cannot be compared to reference program guide information at the central office to infer what programs are associated with the viewing records. Further, the tuning information available from, for example, a frequency detector attachment in communication with a television that is being used to display a previously recorded program does not provide useful tuning information. More specifically, the recorded program is typically supplied by a video recorder (e.g., a VCR) or the like that sends unmodulated low-level video and audio signals to the video and audio inputs of the television that bypass the tuner circuitry of the television.
The use of digital video recorders (DVRs) and personal video recorders (PVRs) such as the TiVo™ system further complicates collection of viewing behavior information because viewers in households with these types of recording devices can rapidly change between live viewing of a program, a somewhat delayed viewing of a program, fast forwarding and rewinding a program, pausing a program, and recording a program for later viewing while watching another program live. The use of processing techniques based on recognition of program signatures has been employed in some cases where it is difficult to obtain accurate tuning information and in cases where it may otherwise be difficult to obtain viewing time information and channel information associated with the currently viewed program content. Unfortunately, these techniques are not well suited for use in situations where a recording device enables rapid changes between live viewing of a program, delayed viewing of the program, viewing of another program while recording the program, etc.